If you're interested in making the max amount of money in the game (999,999), try the following. Just be sure that as you attempt this, you have at least one sellable gem or jewel in your inventory, like a Diamond. It must be unequipped. You must also have access to the Sword Brothers spell (via the Sword familiar).

Now, head to the Library, and go to the location of the Librarian, the game's only merchant. Stand next to his desk and cast Sword Brothers (Down, Down-Right, Right, Up-Right, Up (for two seconds), Down-Attack). If executed correctly, you can then talk to the Librarian as the spell is being cast.

Doing this will glitch the game, allowing you to access your inventory from the Librarian's own menu. Now, remember that unequipped jewel or gem we mentioned earlier? Equip it from this menu, then go to sell that very jewel or gem. However, it won't be sold. Instead, it will duplicate 255 times in your inventory, which you can then sell to the Librarian for massive amounts of gold, including the maximum amount of gold (if you have the patience).

Play as Richter Belmont
After you beat the game once, start a new game and name your file:

RICHTER - You will now play as Richter Belmont!

Better Luck
Beat the game once and then enter the following as your name:

X-X!V''Q - You should then begin the game with 99 luck!

Unlock "Axe Lord" Armor
Beat the game once and then enter the following as your name:

AXEARMOR - You should then begin the game with the Axe Lord armor.

Max Money With Librarian and Sword Familiar
"Required Items/skills

-Sword Familiar
-Gem of any type (Diamond is best choice)
-Enough mana to cast sword brothers spell (50 MP)

Sword Brothers spell:

Enable The Sword Card Familiar
Press the Directional Pad D, DF, F, UF, U(hold UP 2 seconds) D + Attack

Make your way to the Librarians room. Stand near him, but not so you enter
his menu's. Cast the sword brothers spell. As the sword starts to spin,
Walk towards the librarian and enter his menu's. Sell off all but 1 of any
single gem. Press start to enter into alucards menu while still in the
librarian menu's. (Casting of the sword brothers spell allowed you to enter
your menu's while in the librarian's menu's) Have Alucard equip the last gem
of the chosen type. Return to the librarian's menu's and sell the last gem
to the librarian. Since the gem was removed and you sold something you didnt
have for sale, The game drops the count of that gem to 255. Sell off extra
gems to max out your money. I suggest using the diamond to get your money
the fastest."

All Endings
Bad Ending Defeat Richter, while wearing the glasses Maria gave you.

Best Ending: In the battle with Richter, wear the glasses Maria gave you and defeat the green specter. After completing both castles with a percentage of at least 200, defeat the final boss

Good Ending: In the battle with Richter, wear the glasses Maria gave you and defeat the green specter. After completing both castles with a percentage below 150, defeat the final boss.

Worst Ending: Defeat Richter, but don't wear the glasses Maria gave you.